1. Field of the Invention
The present invention relates to a suspension apparatus of an automotive vehicle and, more particularly, to a suspension apparatus of an automotive vehicle, having a liquid cylinder disposed between a member on the vehicle body side and a member of each wheel side and a flow rate control valve so disposed as to alter a suspension characteristic by controlling a supply or discharge of an operating liquid to or from a liquid pressure chamber of the liquid cylinder.
2. Description of Related Art
Heretofore, for example, Japanese Patent Laid-open Publication (kokai) No. 130,418/1988 discloses an active suspension apparatus adapted so as to alter its suspension characteristics by alterring the amount of a liquid disposed in a liquid cylinder by controlling the supply or discharge of an operating liquid to or from the liquid cylinder mounted between a member on the vehicle body side and a member on each wheel side in accordance with the running state of the vehicle. This active suspension apparatus has a flow rate control valve for controlling the supply and discharge of the operating liquid to and from a liquid pressure chamber of the liquid cylinder, an acceleration detecting means for detecting acceleration in the vertical direction, or vertical acceleration, of the vehicle body, an integration means for integrating a signal detected by the acceleration detecting means, and a control means for determining a control amount of the flow rate control valve by multiplying the output signal generated by the integration means with a predetermined gain coefficient. This active suspension apparatus is arranged such that, for instance, when it is confirmed by signals detected by the acceleration detecting means that the vehicle body is rolling, the control signal corresponding to the control amount determined by the control means is generated to the flow rate control valve, thereby subjecting the amount of the operating liquid to be supplied or discharged to or from the liquid cylinder to a PID control and consequently controlling the rolling of the vehicle body.
It is to be noted herein that this active suspension apparatus is so arranged as to improve running stability by executing a reverse roll control by generating a control signal from the control means to the flow rate control valve so as to make the automotive vehicle in a reversely rolling state, when the automotive vehicle lies in a low acceleration region or in a low-speed running state.
The automotive vehicle with the active suspension apparatus having the function of controlling the reverse rolling can provide good driving feeling during ordinary cornering or during one cornering, because the driver can readily confirm the situation of a cornering site or position in a visual way and the driver can stabilize its posture. It has been found, however, that the driving feeling can be rather impaired and the driver may be confused in thinking as if the vehicle is normally rolling and the function of the active suspension would have been damaged, because the posture of the driver changes whenever the vehicle frequently corners in alternating directions during driving along a zig-zag course or the like when the steering wheel is to be frequently steered.
When the automotive vehicle is frequently rolling alternatively in normal and reverse ways, the driver may be confused in thinking as if the vehicle is cornering in a normal fashion without any rolling control and it cannot come to the feeling that the vehicle is rolling actually in a reverse way. Further, the automotive vehicle with the active suspension function may give the driver the impression as if no rolling would happen so much even if the rolling is actually occurring in the reverse way opposite to usual automotive vehicles. Hence, if the driver may come to the wrong recognition that the active suspension function would have been damaged if the vehicle would be rolled in a continuous manner.
It is further to be noted that, in the reverse roll control state, the control should be carried out so as to make the vehicle height on the exterior side of the cornering wheels, upon which a larger load is imposed, higher than the interior side of the cornering wheels, so that a larger driving force is required, as compared with the normal roll control state. Thus, when the reverse roll control is attempted to be carried out in a state in which the steering wheel is steered frequently as in the manner as described hereinabove, more power is consumed for driving the suspension apparatus.